1. Field of the Invention
The present invention relates to a lamination unit of ceramic green sheets, in which a plurality of slits are formed in upper and lower plates composing the lamination unit such that elasticity is provided to the plates.
2. Description of the Related Art
In general, multilayer ceramic electronic parts such as multilayer ceramic substrates, multilayer ceramic condensers (MLCC), multilayer ceramic inductors (MLCI) and so on are manufactured by a process of laminating ceramic green sheets. In this case, the plurality of ceramic green sheets are laminated in a predetermined order and are then pressed into one bar, thereby completely manufacturing a predetermined multilayer ceramic electronic part.
In order to manufacture such a green bar, a molding process, a printing process, a cutting process, a separating process, a laminating process, a pressing process are sequentially performed. In the molding process, ceramic slurry is laid with a thickness of several to dozens μm on a continuous PET film. In the printing process, a predetermined pattern is printed on the surface of the laid ceramic so as to manufacture a ceramic green sheet. In the cutting process, the ceramic green sheet is cut into a predetermined shape for each pattern. In the separating process, the ceramic green sheets cut into a predetermined shape are separated from the PET film. In the laminating process, the ceramic green sheets separated from the PET film are laminated with a predetermined number of layers. In the pressing process, the laminated ceramic green sheets are pressed by predetermined pressure.
Recently, as the capacity of the MLCC is increased and the size of the MLCC is reduced, the thickness of the MLCC should be reduced, and the number of laminated layers should be increased. Therefore, when the MLCC is manufactured, lamination pressure inevitably increases. Accordingly, there is a need for a high-performance laminating device which can transfer and press laminated ceramic green sheets while applying uniform pressure to the laminated ceramic green sheets.
The laminating device is composed of a peeling unit for separating the ceramic green sheets, a lamination unit for laminating and pressurizing the ceramic green sheets, and a cutting unit. Among them, the lamination unit continuously receives high pressure of more than 100 kgf/cm2 at an interval of several seconds. Therefore, components of the lamination unit, such as bolts and so on, may be damaged by continuous vibration caused by a repeated load. When the lamination unit is used for a long term in a state where some of the components are damaged, the balance of a pressurizing surface of the lamination unit is reduced.
Hereinafter, a conventional lamination unit will be described with reference to FIG. 1.
FIG. 1 is a partially-exploded perspective view of a conventional lamination unit used for a ceramic sheet laminating device. As shown in FIG. 1, the lamination unit 10 includes a pair of upper and lower plates 11 and 12, a plurality of posts 13 which support the plates 11 and 12, and a plurality of bolts 14 and buttons 15 for coupling the plates 11 and 12 to the posts 13.
The upper plate 11 of the lamination unit 10 is coupled to the bottom surface of a press 20 provided in the laminating device. As the press 20 is driven, the lamination unit 10 is vertically driven. The lower plate 12, which is supported in parallel to the upper plate 11 by the posts 13, has an MLCC pressing bar 16 attached to the bottom surface thereof. The MLCC pressing bar 16 serves to transfer and laminate ceramic green sheets.
Preferably, the MLCC pressing bar 16 contains a binder for bonding the ceramic green sheets.
In the conventional lamination unit 10 constructed in such a manner, a repeated pressing load of more than 100 kgf/cm2 is applied from the press 20 when the plurality of ceramic green sheets are laminated under the lower plate 12.
The pressing load is transmitted to the lower plate 12 through the posts 13 from the upper plate 11 coupled to the press 20. At this time, the upper and lower plates 11 and 12 and the bolts 14 coupled to the posts 13 supporting the respective plates 11 and 12 may be damaged or released by the pressing load and vibration which are continuously transmitted.
Therefore, when the lamination unit is used for a long term in a state where the fixing portions such as the bolts 40 and so on are damaged, the balance of the lower plate 12, which should press the laminated ceramic green sheets with a uniform load, is reduced. Then, non-uniform pressure is applied to the laminated ceramic green sheets such that the green bar is deformed, which makes it difficult to perform the subsequent processes.
To solve such a problem, spring washers or elastic bodies (rubber or the like) are used in the bolts 14 for coupling the upper and lower plate 11 and 12 to the posts 13, thereby reducing stress applied from the press 20. However, since the spring washers or elastic bodies cannot satisfactorily endure high pressing pressure, it is difficult to apply them to the lamination unit 10.